The patch titled
Subject: mm, memcg: Prevent memory.oom.group load/store tearing
has been added to the -mm mm-unstable branch. Its filename is
mm-memcg-prevent-memoryoomgroup-load-store-tearing.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-memcg-prevent-memoryoomgroup-load-store-tearing.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Yue Zhao <findns94@xxxxxxxxx>
Subject: mm, memcg: Prevent memory.oom.group load/store tearing
Date: Mon, 6 Mar 2023 23:41:35 +0800
Patch series "mm, memcg: cgroup v1 and v2 tunable load/store tearing
fixes", v2.
This patch series helps to prevent load/store tearing in
several cgroup knobs.
As kindly pointed out by Michal Hocko and Roman Gushchin
, the changelog has been rephrased.
Besides, more knobs were checked, according to kind suggestions
from Shakeel Butt and Muchun Song.
This patch (of 4):
The knob for cgroup v2 memory controller: memory.oom.group
is not protected by any locking so it can be modified while it is used.
This is not an actual problem because races are unlikely (the knob is
usually configured long before any workloads hits actual memcg oom)
but it is better to use READ_ONCE/WRITE_ONCE to prevent compiler from
doing anything funky.
The access of memcg->oom_group is lockless, so it can be
concurrently set at the same time as we are trying to read it.
Link: https://lkml.kernel.org/r/20230306154138.3775-1-findns94@xxxxxxxxx
Link: https://lkml.kernel.org/r/20230306154138.3775-2-findns94@xxxxxxxxx
Signed-off-by: Yue Zhao <findns94@xxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Acked-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
Acked-by: Roman Gushchin <roman.gushchin@xxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Muchun Song <muchun.song@xxxxxxxxx>
Cc: Tang Yizhou <tangyeechou@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/mm/memcontrol.c~mm-memcg-prevent-memoryoomgroup-load-store-tearing
+++ a/mm/memcontrol.c
@@ -2067,7 +2067,7 @@ struct mem_cgroup *mem_cgroup_get_oom_gr
* highest-level memory cgroup with oom.group set.
*/
for (; memcg; memcg = parent_mem_cgroup(memcg)) {
- if (memcg->oom_group)
+ if (READ_ONCE(memcg->oom_group))
oom_group = memcg;
if (memcg == oom_domain)
@@ -6623,7 +6623,7 @@ static int memory_oom_group_show(struct
{
struct mem_cgroup *memcg = mem_cgroup_from_seq(m);
- seq_printf(m, "%d\n", memcg->oom_group);
+ seq_printf(m, "%d\n", READ_ONCE(memcg->oom_group));
return 0;
}
@@ -6645,7 +6645,7 @@ static ssize_t memory_oom_group_write(st
if (oom_group != 0 && oom_group != 1)
return -EINVAL;
- memcg->oom_group = oom_group;
+ WRITE_ONCE(memcg->oom_group, oom_group);
return nbytes;
}
_
Patches currently in -mm which might be from findns94@xxxxxxxxx are
mm-memcg-prevent-memoryoomgroup-load-store-tearing.patch
mm-memcg-prevent-memoryswappiness-load-store-tearing.patch
mm-memcg-prevent-memoryoom_control-load-store-tearing.patch
mm-memcg-prevent-memorysoft_limit_in_bytes-load-store-tearing.patch
